1. Field of the Invention
The present invention relates generally to a bearing (direction) sensor and a bearing-distance sensor, and more particularly to a bearing sensor and a bearing-distance sensor for use in a car navigation system, for example, the bearing sensor being capable of detecting a travel bearing of a vehicle, and the bearing-distance sensor being capable of detecting both a travel bearing and a travel distance of the vehicle.
2. Description of the Related Art
There exists a car navigation system using a bearing sensor for detecting a travel bearing and a distance sensor for detecting a travel distance. There are also two types of bearing sensors; one using a vibratory gyroscope and another wherein two acceleration sensors are disposed horizontally with a wide space therebetween. The bearing sensor using the vibratory gyroscope detects an angular velocity of rotation by means of the vibratory gyroscope and determines a travel bearing from the angular velocity of rotation. The bearing sensor in which two acceleration sensors are disposed horizontally detects accelerations at two locations by means of those two acceleration sensors and determines a travel bearing from a difference of those accelerations.
However, because the vibratory gyroscope is expensive, the navigation system in which the bearing sensor uses the vibratory gyroscope also becomes expensive.
On the other hand, the navigation system with the bearing sensor having two acceleration sensors disposed horizontally is too large, because those two acceleration sensors have to be disposed horizontally in an adequate space within the system.
Accordingly, it is an object of the present invention to provide a small and inexpensive bearing sensor which can detect a travel bearing of a vehicle.
It is another object of the present invention to provide a small and inexpensive bearing-distance sensor which can detect a travel bearing and a travel distance of a vehicle.